Commercial aircraft must not only meet strength, weight and cost objectives they must also be designed to achieve adequate customer satisfaction. One arena of customer satisfaction arises regarding passenger comfort. The reduction of interior noise levels is considered critical to passenger comfort. A wide variety of noise sources come from many locations outside and inside the airframe. Aircraft design benefits are achieved by addressing these noise sources and minimizing their impact on passengers.
One known noise source into the main cabin is through the aircraft floor panels. The floor panels are typically constructed using lightweight designs with high rigidity. These very light weight structural solutions are typically not efficient at reducing noise that transmits through them. Because the floor panels are stiff, they have fast traveling bending waves which tend to match well with acoustic waves which produce a low coincidence frequency. The floor panels, therefore, have a high radiation efficiency which is bad for interior noise.
A current methodology for dealing with such resonant floor panels is through the use of add-on damping patches bonded to the underside of the floor for the purpose of increasing damping. This approach adds extra weight, fabrication costs, and installation costs to the floor panel design.
What is needed is a design and method for increasing damping in floor panels that was more weight and cost effective than current add-on damping techniques. Additionally, it would be highly desirable to have a design and method for such floor panels that simplified the time and complexity of fabrication.